What did John MacAdam invent?

John MacAdam invented a new type of road, known as the Macadam, which revolutionized road construction in the early 19th century. Macadam roads used large, broken stones in symmetrical patterns, covered with small stones, to create a hard surface.

MacAdam's design forms the basis for modern tarmac roads. A wealthy Scottish estate owner who was named road trustee of his local district, MacAdam noted the roads were in terrible condition and funded his own experiments to improve them. MacAdam's innovations proved so successful that they were adopted in many countries, including England and the United States. In 1827, MacAdam was appointed Surveyor General of Metropolitan Roads in England.